The present invention relates to a surface-mount device and to a method for manufacturing the surface-mount device.
FIGS. 7 and 8 show a conventional light-emitting device as a surface-mount device (SMD). The light-emitting device 110 comprises an LED 101 mounted on a substrate 102 as an electronic element, electrodes 103 and 104, each formed on the upper surface, side wall, and underside of the substrate 102. The cathode 101c of the LED 101 is directly connected to the electrode 103, and the anode 101a is connected to the electrode 104 by a bonding wire 106. The LED 101, bonding wire 106 and electrodes 103 and 104 are covered by a protector layer 107. The light-emitting device 110 is manufactured together with a number of other light-emitting devices on a substrate aggregation and cutoff from the adjacent substrate 102a at an elongated through-hole 105.
On the other hand, the protector layer 107 is formed by injecting a liquid resin in a mold mounted on the substrate 102. In order to prevent the liquid resin from entering the through-hole 105, the protector layer 107 must be formed at a position away from the through-hole 105. As a result, the size of the substrate becomes large.
A light-emitting device 120 shown in FIGS. 9 and 10 dissolves the above described problem.
The light-emitting device 120 comprises an LED 121 mounted on a substrate 122, electrodes 123 and 124. The substrate 122 has a pair of grooves 122a and 122b, each having a semicircular section, at opposite sides thereof. The upper side and underside portions of the electrode 123 (124) are connected to each other by a connector portion 123a (124a) formed in the groove 122a (122b).
Each of the grooves 122a and 122b is closed by a dry film 125 at the upper opening. The whole upper surface is sealed by a protector layer 127. The dry film 125 prevents the material of the protector layer 127 from entering the groove 122a (122b).
In the light-emitting device, the electrode is not projected from the protector layer 127. Therefore, the size of the device is reduced. However if the dry film 125 does not exist, the device can be more miniaturized.
A light-emitting device 130 of FIGS. 11 and 12 is to achieve such an aim.
The light-emitting device 130 comprises an LED 131 mounted on a substrate 132, and a pair of electrodes 133 and 134. Each of the electrodes comprises an upper electrode 133a (134a) of copper foil, a lower electrode 133b (134b) of copper foil, and a connecting layer 133c (134c) formed in a groove 132a (132b). A protector layer 137 seals the LED 131 and others.
A method of forming the electrode 133 will be described hereinafter with reference to FIGS. 13a to 13d. 
Referring to FIG. 13a, the upper electrode 133a and lower electrode 133b are formed on upper and lower sides of the substrate 132 with copper foil. A part of the lower electrode 133b is removed at a position corresponding to the groove 132a by etching as shown in FIG. 13b. A part of the substrate 132 is removed to form the groove 132a by laser processing as shown in FIG. 13c. Next, the connecting layer 133c is formed on the surfaces of the groove 133a, the underside of the upper electrode 133a and the underside of the lower electrode 133b as shown in FIG. 13d. 
The light-emitting device 130 can be made into a small size compared with the light-emitting device 120 of FIG. 9, since the dry film is not provided. However, since the groove 132a of the device 130 is formed by the laser processing, the manufacturing cost increases.
An object of the present invention is to provide a light-emitting device which may be made into a small size at a low cost.
According to the present invention, there is provided a surface-mount device comprising a substrate, having a pair of grooves, each communicating an upper surface and a lower surface with each other, a pair of electrodes, each of which comprises an upper electrode and a lower electrode, a connecting layer formed on an inside wall of each of the grooves to electrically connect the upper electrode and the lower electrode with each other, an electronic element mounted on one of the electrodes, a lid provided in an upper portion of each of the grooves, a protector layer formed on the substrate to seal the upper electrode, electronic element and lids.
The lid is made of resist material, and the electronic element is an LED.
The grooves are formed in opposite sides of the substrate.
The present invention further provides a method for manufacturing a surface-mount device, comprising the steps of preparing a substrate aggregation having a plurality of substrate divisions, and through-holes between adjacent substrate divisions, forming a pair of electrodes, each comprising an upper electrode and a lower electrode on an upper surface and a lower surface of the substrate division, forming a connecting layer on an inside wall of through-hole for electrically connecting the upper and lower electrodes, mounting an electronic element on one of the upper electrodes, closing an upper opening of the through-hole by a lid, sealing the electronic element, the upper electrodes and lids with a protector layer, and cutting off each of the substrate divisions from the substrate aggregation at through-holes.
The lid is formed by charging a resist material in the through-hole, solidifying an upper portion of the charged resist material, and removing a non-solidified portion from the through-hole.
These and other objects and features of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings.